Originally posted by Nightwolf:
0401 and 0402 EGR insufficient and excessive at the same time i have heard this can mean the DPFE sensor. and what does DPFE stand for? 
DPFE - Differential Pressure Feedback EGR (Exhaust Gas Recirculation). It is also known as the EGR Backpressure Transducer.
While it could be a faulty DPFE sensor, I would suggest testing it first. This thread has the how to for P0402.
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=trouble&Number=1261255&page=2&view=collapsed&sb=5&o=31&fpart=1
In addition, from Ford CD manual, P0401.
Diagnostic Trouble Code (DTC) P0401 indicates that Continuous Memory Self-Test has detected insufficient EGR flow.
Possible causes:
-- EGR valve stuck closed or iced.
-- EGR valve diaphragm leaks.
-- EGR valve or flow path restricted.
-- EGR vacuum hose off, plugged or leaks.
-- VPWR circuit open to EGR Vacuum Regulator (EGR V.R.) solenoid.
-- EVR circuit to PCM open.
-- EVR circuit to PCM shorted to PWR.
-- Differential Pressure Feedback EGR (D.P.F. EGR) sensor pressure hoses both off.
-- D.P.F. EGR sensor pressure hoses reversed.
-- D.P.F. EGR sensor VREF circuit open.
-- Downstream pressure hose off.
-- Downstream pressure hose plugged.
-- Damaged orifice tube assembly.
-- Damaged EGR V.R. solenoid.
-- Damaged D.P.F. EGR sensor.
-- Damaged PCM.
Last edited by Tony2005; 06/20/06 12:35 AM.
